The invention relates to starch used in the food-industry.
Foodstuff is often thickened by the inclusion of a certain amount of starch as binder, filling or thickening agent, for example providing viscosity to a foodstuff during automated filling (canning).
For example, when industrially autoclaving or sterilising a food-stuff containing solid pieces, a certain filling viscosity is required while a container is being filled to prevent splashing of the liquid content over the rim of the container. Also, said viscosity provides an equal distribution of said solids during the filling phase. In canning, after filling, a decrease of viscosity is required, and any residual viscosity of the foodstuff after filling is considered unwanted for many applications. However, viscosity of starches in general is reduced during or after prolonged heat treatment, said reduction is in general aggravated by the presence of salts in the foodstuff.
Yet another reason to thicken a foodstuff is to provide said food with a better flavour, texture (mouthfeel) and appearance (looks).
Starch in itself has some flavour, that in general is appreciated by a customer, provided the foodstuff does not comprise too much starch which makes it taste starchy or cereal-like and provided a sensation of well-cooked starch is present, as opposed to an xe2x80x9cundercookedxe2x80x9d starch which gives a raw sensation. Most flavour in food, however, derives from (intricate combinations of) salts, proteins, short peptides, amino acids, fatty acids and salts thereof, sugars, short and medium chain alcohols, and so on.
Texture of a starch comprising food is very much dependent on the degree of viscosity attained by adding varying degrees of starch. Aspects such as smoothness, firmness, cohesiveness, density, thickness, wateriness, cutability or spreadability, chewability and others can all depend on the viscosity and water retention properties provided by a starch. Too much cohesiveness is in general not appreciated, customers often prefer a more creamy, smooth texture. The choice of type of starch for use in foodstuff is greatly influenced by properties such as the stability during baking, deep-freezing, thawing and storage. It must furthermore be remembered that in general too much starch, although providing a desired viscosity, may change the flavour of the food negatively, in general there is a need to reduce starch dosage whenever this is made possible.
Appearance of a starch comprising foodstuff relates among others to the aspects mentioned with texture, however, starches often add opacity or cloudiness to food, making it look less palatable.
The above illustrates that, within the food industry, use of starch, for each and every different application, often comprises finding the right balance between too little and too much, in trying to find a product with attractive palatability.
A distinct problem herein is the fact that starches in themselves have reduced stability to the effects of certain salts, ions or electrolytes present in food. For example, a starch may initially provide a desired texture (such as smoothness, firmness, cohesiveness, density, thickness, wateriness, curability or spreadability, chewability) to a foodstuff, which than, however, looses said texture, cohesiveness or smoothness in time because the salt-stability of the starch used is too low or inappropriate. The product becomes watery, falls apart and separates into wet and less wet fractions, leaks flavours, in general looses its appearance and texture, and looses its attraction to a customer. Said loss of texture or appearance is in general caused by a too low stability to salts, electrolytes, cations or anions, or other constituents of food, and necessitates increasing the starch dosage, often with detrimental effects on taste.
The effects of salts on starch have been investigated for more than a century (see for examples: Starch: Chemistry and Technology. Eds. Whistler and Paschall, Academic Press, New York and London).
The gelatinization of starch and starch derivatives in the presence of medium to high concentrations of electrolytes has been studied extensively (B. J. Oosten, Die Staerke 31, 228-230 (1979); B. J. Oosten, Die Staerke 32, 272-275 (1980); B. J. Oosten, Die Staerke 34, 233-239 (1982); B. J. Oosten, Die Staerke 35, 160-169 (1983); B. J. Oosten, Die Staerke 42, 327-330 (1990)). In low concentration systems the properties of solutions of polymers in the presence of electrolytes can be adequately accounted for by electrostatics, taking into account only the magnitude of the ionic charge, the concentration and the solvent. Biological systems are usually more concentrated and specific ion-solvent effects will dominate the solution properties
Some electrolytes promote gelatinization and some electrolytes inhibit the process. Promotion or inhibition mainly follow the well known Hofineister or lyotropic series (F. Franks in xe2x80x9cWaterxe2x80x9d, Royal Society of Chemistry Paperbacks London 1983). This series are a listing of the order in which they affect polymer (and therefor starch) solubility. An example of such a series is:
CNSxe2x88x92 greater than ClO4xe2x88x92 greater than Ixe2x88x92 greater than NO3xe2x88x92 greater than Clxe2x88x92 greater than Fxe2x88x92 greater than HPO32xe2x88x92 greater than SO42xe2x88x92, 
Electrolytes on the left (CNSxe2x80x94, C104xe2x80x94, Ixe2x80x94, NO2xe2x80x94) promote and on the right (Clxe2x88x92, Fxe2x88x92, HPO32xe2x88x92, SO42xe2x88x92) inhibit gelatinisation.
This series can of course be extended with other anions and similar series can be listed for cations, although in general the effects observed for cations are smaller than for anions. A completely satisfying explanation for the observed phenomena for this series has not been reported so far, but the general believe is that electrolytes on the right side enhance water structure thus favouring solventxe2x80x94solvent interactions over starch-solvent interactions (Franks 1983). This induces a hampered gelatinisation and lack of stability of starches in water.
Neutral components, such as hydrocolloids, ureum, sorbitol, caseine, and sugars such as sucrose, fructose, galactose, and others have similar effects on the stability of starch as salts. It has for example been found that neutral components like saccharides (sugars) effect the viscosity of strach and derivatives (I. D. Evans, D. R. Haisman, Die Staerke 34, 224-231 (1982)). The effects have been contributed to the same phenomena as seen with salts, notably the effects reported on water structure are similar.
The application of starch derivatives in food systems is usually accompanied by the addition of electrolytes, mainly chlorides and phosphates. Especially chlorides and phosphates inhibit the development or stability of viscosity of starch and starch derivatives.
A special case is the addition of calcium ions to potato starch and potato starch derivatives. Potato starch contains bound monophosphate ester groups. In water these phosphate groups give the starch backbone negative charge resulting in a high viscosity as compared to other starches. When calcium ions are added they form a relatively insoluble complex with the phosphate groups resulting in a sharp decrease in viscosity.
Thus, although salt-instability of starch is relatively well understood, the problem remains, starches currently used in the food-industry generally have low-stability to salts compromising at least the palatibility, texture, appearance and other related aspects of foodstuffs.
The invention provides modified starch, and derivatives derived thereof, having improved salt-stability (salt-stable starch), use of such modified starch or derivatives derived from said starch in foodstuff, a method for providing salt-stability to foodstuff comprising use of such modified starch or derivatives derived from said starch and foodstuff comprising said modified starch or derivatives derived from said starch.
The invention provides a method for improving a foodstuff comprising adding to said foodstuff a salt-stable starch. Such a starch has improved stability to salts and other components that are detrimental to the stability of a common starch. The invention for example provides a method for improving the texture of a foodstuff, e.g. the cohesiveness of relatively solid foods such as meats or meat products or puddings or the smoothness of relatively liquid products such as soups, sauces, creams or fillings. The invention provides a method wherein said salt-stable starch is a non-cereal starch, for example derived from tubers or roots containing essentially only mylopectin molecules.